1. Field of the Invention
This invention relates generally to the field of consumer packaging, and more specifically to metal cans, such as the steel and aluminum cans that are commonly used for packaging soft drinks, other beverages, food and aerosol products.
2. Description of the Prior Art and Recent Technology
Metal cans for soft drinks, other beverages and other materials are of course in wide use in North America and throughout the world. The assignee of this invention, Crown Cork & Seal Company of Philadelphia, is the world's largest designer and manufacturer of such cans.
The art of making and packing metal cans is constantly evolving in response to improved technology, new materials, and improved manufacturing techniques. Other forces driving the evolution of technology in this area include raw material prices, the nature of new materials to be packaged and the marketing goals of the large companies that manufacture and distribute consumer products such as soft drinks.
Interest has existed for some time for a metal container that is shaped differently than the standard cylindrical can in such a distinctive way to become part of the product's trade dress, or to be otherwise indicative of the source or the nature of the product. To the inventors best knowledge, however, no one has yet developed a practical technique for manufacturing such an irregularly shaped can at the volume and speed that would be required to actually introduce such a product into the marketplace.
Attempts have been made to manufacture shaped cans. Several decades ago, perhaps in the 1960's or early 1970's, Continental Can Company was reputed to have developed a technique for steel cans that involved expanding a rubber mandrel or balloon that is inserted into the can shell, which caused the can shell to expand against an outer mold. Diadavantages of this method include limited balloon lifetime, limited production speed, and a relatively high level of complexity.
More recently, Carnaud MetalBox PLC has developed a technique for shaping metal cans that involves placing the unshaped can in a die and then causing combustion to take place in the can. The intense heat and pressure of the combustion drives the sidewall of the can against the die, shaping the can. Disadvantages include the production of combustion by-products, and the possibility of fire risk at the production site.
A need exists for an improved system and process for manufacturing a shaped metal can, that is effective, efficient and inexpensive, especially when compared to technology that has been heretofore developed for such purposes.